This invention relates to a molten carbonate fuel cell, and in particular to a molten carbonate fuel cell wherein the collector plate and/or the interconnector thereof is improved.
Various kinds of fuel cells have been proposed and commercially utilized. Among them, a molten carbonate fuel cell is now extensively studied and being developed because it is advantageous in power generation efficiency as well as it is capable of utilizing coal gas as a fuel gas.
This molten carbonate fuel cell is constructed such that a plurality of unit cell, each comprising an anode (a fuel electrode), a cathode (an air electrode) and an electrolyte body, are superimposed one upon another with a collector plate being interposed between the unit cells, and an interconnector is interposed between the collector plates to partition the unit cells. There is also disposed in the fuel cell a separator comprising a couple of edge-sealing plates for holding therebetween the peripheral portion of the electrolyte body. Thus, these edge-sealing plates are contacted with the peripheral portion of the electrolyte body so as to form a wet seal and to shield the unit cells from the outer atmosphere.
By the way, the collector plate (in particular, which is disposed on the oxidizing gas-side) and the interconnector are rendered to be covered with a film of highly corrosive molten carbonate solution which has been exuded from the air electrode during the operation of the fuel cell. Because of this, the collector plate is conventionally formed of stainless steel having an excellent corrosion resistance. The stainless steel conventionally employed is mainly SUS310S and SUS316L.
However, the collector plate formed of stainless steel is accompanied with a problem that a corrosion product layer exhibiting a high electric resistance is caused to deposit on the surface of the collector plate during the operation of the fuel cell. Therefore, when the fuel cell is operated for a long period of time extending over 1,000 hours, the deposition of corrosion product layer is grown up increasing the electric resistance thereof. Since the electromotive force which is output from the fuel cell is directly influenced by a contact resistance between the collector plate and the interconnector, any increase in contact resistance would lead to a prominent deterioration of the performance of the fuel cell. Namely, the deposition of the corrosion product on the collector plate or interconnector becomes a hindrance in improving the performance and life of a fuel cell.